1. Field of the Invention
The invention relates in general to ophthalmic lenses and, more particularly to contact lenses, both of the rigid and soft type having surface structures on at least one surface thereof.
2. Description of the Prior Art
Contact lenses are frequently used to correct refractive error of the eye. Overwhelmingly, contact lenses are used to correct the vision of humans, but occasionally contact lenses are also applied on animal eyes.
Early contact lenses were made of rigid plastics. The majority of present day contact lenses are made of soft hydrogels, since soft contact lenses generally offer superior wearing comfort. Still, rigid lenses are used by a sizeable portion of the population because of ease of handling and due to certain kinds of refractive error (e.g. astigmatism) being more readily corrected by rigid lenses.
Lens comfort is an issue with both rigid and soft contact lenses. Lens comfort is largely determined by the lens-eye-configuration, and, in particular, by the presence and amount of tear fluid between the lens surface and the cornea as well as by the tear layer on the front surface of the lens.
The surfaces of all present contact lenses are substantially smooth, and care is taken to eliminate any surface alterations on both the front and the back surfaces of standard monofocal contact lenses. The only exception are bifocal diffractive lenses which usually exhibit minor steps on the back surface. This applies both for rigid and soft contact lenses. With rigid contact lenses, a smooth surface is achieved e.g. by polishing. The cornea surface is also a smooth surface. Consequently, the tear layer has to provide lubrication between two smooth surfaces.
Therefore, a limitation of currently available contact lenses is a potential breakdown of tear fluid between the cornea surface and the contact lens making the lenses uncomfortable to wear and/or requiring the wearer to use lubricating eye drops. The present invention is directed to a contact lens which provides enhanced comfort and better lubrication between the cornea surface and lens surface.